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Special Issue on Individual heterogeneity

We are very proud to announce the publication of our Special Issue “Individual heterogeneity: the causes and the consequences of a fundamental biological process”. This Special Issue originated from a workshop we held at UiT The Arctic University of Norway in Tromsø, in October 2015. The workshop was initiated at the end of a large collaborative project aiming at quantifying individual heterogeneity and its influence on life-history trajectories over age. The more the project was going forward, the more it prompted new questions and perspectives on this very broad and diverse concept of individual heterogeneity. Indeed, because individual heterogeneity in life-history traits drives selection and maintains adaptation, topics like individual heterogeneity, life-history theory, population dynamics, and evolutionary ecology have now become cross-cutting themes for many ecologists. The fundamental significance of this biological process, however, is not evenly acknowledged across different disciplines, and the approaches taken vary widely.

This stimulated us to bring together researchers working on individual heterogeneity across disciplines to explore the importance of individual heterogeneity with multiple eco-evolutionary perspectives. Our goal was to discuss both theoretical and methodological developments, as well as analyzing empirical case studies across the tree of life, from bacteria to mammals (Figure 1). The discussions we held at the workshop allowed progressing further on individual heterogeneity, leading to the production of this Special Issue dedicated to this timely topic.

The Special Issue is a balanced mix of reviews and empirical papers synthesizing current understanding and perspectives on individual heterogeneity, with three specific aims:

Review and present new methodological developments on how to measure individual heterogeneity and to quantify its influence on life-history trajectories and population dynamics,
Assess the origins and maintenance of individual heterogeneity and its impacts on life-history trajectories,
Determine how individual heterogeneity shapes population dynamics and eco-evolutionary interactions within and among species, with an emphasis on the role played by neutral variation.

The discussions we had during the workshop provided the opportunity for authors to incorporate various perspectives, thereby producing comprehensive and outstanding contributions for the Special Issue. In addition, reflections on emerging issues and on areas requiring further developments to move forward were discussed and are reported in the general conclusion, which gathers the perspectives of most contributors to the Special Issue.

We sincerely hope you will enjoy reading our Special Issue on individual heterogeneity and we look very much forward to follow future researches that will emerge on this fascinating topic.

Sandra Hamel, Jean-Michel Gaillard and Nigel Yoccoz

The figure illustrates some of the species used as case study in the Special Issue on individual heterogeneity. From top left to bottom right:

Individual heterogeneity among clonal bacteria grown under identical environmental conditions in growth channels of a microfluidic chip. Heterogeneity becomes evident by differences in survival and growth: green bacteria cells are alive, red cells are dead. Note also difference in size of cells, illustrating differences in size at division and related difference in division frequency (i.e. reproduction). See paper by Jouvet et al. (2018). Image credit: U. Steiner.
Individual heterogeneity in terms of alternative reproductive tactics in the bulb mite Rhizoglyphus robini, where males adopt one of two alternative strategies to mate with females: males are either large, armed fighters (left) or small, benign sneakers (right). See paper by Smallegange et al. (2018). Photo credit: I.M. Smallegange.
Two garter snakes Thamnophis elegans of different life-history ecotypes from populations around Eagle Lake (California, USA). Even within this system of well-characterized differences among populations, there is significant among-individual heterogeneity in growth and survival within populations. Gangloff et al. (2018) describe how maternal physiology and behaviour interact to shape these trajectories in their offspring. Photo credit: Stevan Arnold.
Two uniquely identified common terns Sterna hirundo sitting on a registration box located in the Banter See (Wilhelmshaven, Germany). Individual marking combined with registration boxes and observations allows following the life-history of individuals from birth to death, offering the opportunity to study life-long effects of individual heterogeneity. See paper by Vedder and Bouwhuis (2018). Photo credit: S. Bouwhuis.
Three individually marked bighorn sheep rams Ovis canadensis lined up outside the trap at Ram Mountain (Alberta, Canada) in early June. This long-term study following individuals from birth to death allowed assessing covariance in terms of growth, reproductive success, and survival, and thereby identifying three main life-history tactics among males. See paper by Hamel et al. (2018). Photo credit: M. Festa-Bianchet.

Oikos Journal

Oikos is a journal issued by the Nordic Ecological Society and is one of the leading peer-reviewed journals in ecology. Oikos publishes original and innovative research on all aspects of ecology, defined as organism-environment interactions.